Imaging of a subject from a plurality of different viewpoints is being performed in various technological fields. Examples include stereo cameras, which images a subject from left-eye and right-eye viewpoints and generate a three-dimensional picture from the left-eye-viewpoint and right-eye-viewpoint images, and twin-lens stereoscopic, electronic, three-dimensional image pickup apparatuses. The “twin-lens stereoscopic” refers to a technology for measuring the position or the like of a mobile object, such as a vehicle, robot, or animal, and is a technique by which such as the distance from the image pickup apparatus to the mobile object is obtained from a picture obtained by imaging the mobile object from different angles using a plurality of image pickup units included in the image pickup apparatus and from a parameter, such as the focal length of the lens of each image pickup unit or the distance between the image pickup units, according to the principle of triangulation.
Image pickup apparatuses as described above are required to synchronize the timings at which the image pickup units start exposures. For example, in an image pickup apparatus disclosed in Patent Literature 1, as shown in FIG. 10, a sensor drive signal generation unit 34 generates a sensor drive signal and outputs it to a first CCD image pickup unit 12 and a second CCD image pickup unit 22 to cause the two image pickup units to perform exposures simultaneously. Note that FIG. 10 is generated by changing the reference signs of FIG. 1 of Patent Literature 1.
An image pickup apparatus disclosed in Patent Literature 2 also synchronizes the timings at which two image pickup units start exposures, by providing an exposure start timing signal provided to one image pickup unit, as well as to the other image pickup unit.
In the following description, a control signal for causing an image pickup unit to start an exposure, such as the sensor drive signal or exposure start timing signal, will be referred to as an exposure start signal.